linux-kernel - Re: [PATCH 2/2] perf test: Improve pmu event metric testing

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Message-ID: <CAP-5=fWt58UVTTj_qvirMhMOaUbur+HzxrTi5u1qvCA1ft9BEw@mail.gmail.com>
Date:   Thu, 14 May 2020 16:02:49 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     John Garry <john.garry@...wei.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Paul Clarke <pc@...ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/2] perf test: Improve pmu event metric testing

On Thu, May 14, 2020 at 2:00 AM John Garry <john.garry@...wei.com> wrote:
>
> On 13/05/2020 17:10, Ian Rogers wrote:
> >> Out of interest, if we could move the validation of metrics to jevents,
> >> how much functionality would we still have here?
> > If we add checking to jevents then the MetricExpr would be known to be
> > valid, however, the events (aka ids) within the expression could be
> > invalid.
>
> So I think that has some value. I mean, just to detect syntax errors,
> like those remedied in "perf metrics: fix parse errors in power8 metrics".
>
> > I'm not sure we could realistically check the events at
> > jevents (build) time as there is no guarantee that the machine we run
> > on is the same as the one we compile on.
>
> But we could at least check that there are event aliases for that CPU,
> right? (by examining the JSONs for that cpu). If the event alias does
> not actually match on the target CPU, then that can't be helped.

Agreed, I think there will be some cases where something more can be
done. Jiri has proposed fake pmus as well:
https://www.spinics.net/lists/linux-perf-users/msg11760.html
I don't know how much sense it makes trying to get this in jevents, as
long as 'perf test' is run.

Thanks,
Ian

> Cheers,
> John
>